Stabilized middle distillate fuels



fastest Patented Dec. ii, men

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3,063,034 STABHLEZED MmDlLE DESTHLLATE FUELS John V. Clarke, 3n,@ranford, and Stephen 3. Metro, Elizabeth, NJL, and John 8. Smith, in,Swampscott, Mass, assignors to Ease Research and Engineering Company, acorporation of Delaware No Drawing. Filed Nov. 8, 1957, Ser. No. 695,2218 flairns. (Ci. 44-72) The present invention relates to improvedhydrocarbon oils and more particularly relates to improved petroleumdistillate fuels stabilized against deterioration during storage by theincorporation therein of small amounts of certain tetraalkyl ammoniumsalts of phosphosulfurized hydrocarbons.

The unstable characteristic of petroleum distillate fuels such asheating oils, diesel fuels, jet engine fuels and similar fuel productsboiling in the range between about 300 F. and about 900 F. often giverise to serious difliculties. Such fuels generally contain small amountsof unsaturated hydrocarbons and other relatively unstable constituents.During storage of the fuels these unstable materials tend to oxidize,polymerize or otherwise react to form sludge and sediment. When thefuels are subse quently introduced into engines and burner systems,sludge and sediment thus formed is frequently responsible for theplugging and clogging of fuel lines, filter-s, orifices and the like.

The use of additive agents to overcome or at least arneliorate thesedifliculties is Well known and has been widely practiced. The additivesfound most effective and most widely used in the past have been metalliccompounds such as metal naphthenates, metal sulfonates, metal salts ofalkyl metal sulfides and similar materials which leave a residue whenburned. It is known that the use of such additives leads to a build-upof carbonmetallic deposits in combustion chambers and on burner nozzles.Various ashless compounds have been proposed for use as stabilizingagents in such fuels in order to avoid the formation of deposits of thistype but in general such materials have not been highly effective.

The present invention provides a class of improved additive materialsfor use in petroleum distillate fuels which, when added thereto in smallamounts, effectively stabilize such fuels against deterioration andpermit their storage for extended periods under adverse conditions. Inaccordance with the invention it has been found that certain tetraalkylammonium salts of phosphosulfurized hydrocarbons can advantageously beemployed as stabilizing additives for petroleum distillate fuels boilingin the range between about 300 F. and about 900 F. and that such saltshave advantages not possessed by additive materials employed in thepast.

The tetraalkyl ammonium salts of the phosphosulfurized hydrocarbonsemployed as stabilizing additives in accordance with the presentinvention are prepared by first reacting a hydrocarbon with a sulfide ofphosphorus to form an acidic product and then reacting the productobtained with a tetraalkyl ammonium hydroxide having alkyl groupscontaining from 1 to about 4 carbon atoms. It is believed that theactive ingredient of the material thus formed is an alkyldithiophosphonic acid salt having the following structural formula:

where R is-a hydrocarbon radical and R is an alkyl group containing from1 to about 4 carbon atoms. These compounds are ashless and have theadded advantage of being ionic materials. This latter characteristic isof particular importance in that ionic compounds added to such fuelsassist in dissipating static electricity built up in the fuels as theyare pumped through pipelines and into storage vessels. Numerousexplosions have occurred recently as a result of static build-up indistillate fuels. Ionic additives alleviate the danger of suchexplosions.

A wide variety of hydrocarbon materials including parafiins such asthose obtained by dewaxing lubricating oils; olefins such asisobutylene, decylene, dodecylene, octadecylene and the like; polymersof low molecular weight olefins; and petroleum fractions such aslubricating oils and bright stocks may be used in preparing thephosphosulfurized hydrocarbons from which the additive materials of theinvention are made. Olefinic polymers having molecular weigh-ts rangingfrom about 800 to about 20,000 and petroleum bright stock fractions arepreferred hydrocarbon materials for the purpose of the invention.

The olefinic polymers from which the phosphosulfurized hydrocarbons usedin preparing the additive agents of the invention are produced areprepared by the polymerization of low molecular'weight olefins such asethylene, propylene, butylene, isobu-tylene or combinations of sucholefins. One method of carrying out such polym erization reactions is toemploy a Friedel-Crafts catalyst such as boron trifluoride or aluminumtrichloride at low temperatures in the range of from about 0 F. to about.40 F. Other methods familiar to those skilled in the art may also beused. Polybutene having a molecular weight between about 800 and about10,000 is particularly preferred olefinic polymer for use in accordancewith the invention. In the petroleum industry polybutene isconventionally understoodto mean polyisobutylene and is so used here. pp

The bright stocks which may be used in preparing the phosphosulfurizedhydrocarbons are conventional products of petroleum refining. They arerefined petroleum fractions which are high viscosity lubricating oils.Such stocks are conventionally prepared by first deasphalting thereduced crude oil and then dewaxing it, following this with phenolextraction and sulfuric acid treating, and finally clay filtering theoil as a finishing step. Such bright stocks generally have viscositiesin the range of from about 145 to about 155 Saybolt Universal seconds at210 F. The A.P.I. gravity of such stocks may range from about 25 toabout 28. Their color may vary from about 3 to about 4 /2 on theRobinson scale.

The sulfide of phosphorus which is employed in preparing thephosphosulfurized hydrocarbon may be P 8 P 5 P 8 P 8 or a similarphosphorus sulfide. Phosphorus pentasulfide, P 8 is preferred as aphosphosulfurizing agent.

The phosphosulfurization reaction may be effected by treating thehydrocarbon with from about 5% to about 20% of the phosphorus sulfide byweight, based on the oil. It is usually preferred to add the phosphorussulfide to the oil in powdered form at a temperature in the range offrom about 200 F. to about 250 F. and then heat the mixture to thereaction temperature, about 300 to about 550 F. Agitation should beprovided during the addition of the phosphorus sulfide to insurecomplete mixing. The

mixture is held at the reaction temperature for a period of from about 2to about 10 hours and at the end of that time is filtered to obtainthephosphosulfurized hydrocarbon product. 7 v

The tetraalkyl ammonium hydroxide which is reacted with thephosphosulfurized. hydrocarbon prepared as described above may be onehaving alkyl groups containing from 1 to about 4carbon atoms. Tetraethylammonium hydroxide is particularly preferred for purposes of theinvention.

3 The reaction of the tetraalkyl ammonium hydroxide with thephosphosulfurized hydrocarbon to obtain the additive materials of theinvention may be carried out by reacting equimolar quantities of the twomaterials in the presence of a suitable solvent such as benzene. It ispreferred to employ the tetraalkyl ammonium hydroxide in the form of anaqueous solution of from about to concentration. The reaction may becarried out in a side arm refluxing apparatus for ease of water removal.The mixture containing the reactants is refluxed at a temperaturebetween about 150 F. and about 200 F. for a period of from about 2 toabout 6 hours. The water initially present and water formed during thereaction is driven off as the mixture is refluxed. The benzene added asa solvent is then removed by vacuum distillation and the tetraalkylammonium salt of the phosphosulfurized hydrocarbon is recovered.

The petroleum distillate fuels in which the additive materials of theinvention are employed are those which boil in the range between about300 F. and about 900 F. Typical of such fuels are heating oils fallingwithin grades 1 and 2 of ASTM Specification D-396-48T, diesel fuelsmeeting the requirements for grades 1D, 2D, and 4D fuels as set forth inASTM Specification D-975-53T and jet engine fuels such as those definedby U.S. Military Specifications MIL-iF-5624C and MIL-F-5616. Theadditive materials of the invention may be incorporated into such fuelsin concentrations ranging from about 0.001% to about 5% by weight,preferably 0.001 to 2% by weight.

Concentrations of from about 0.005% to about 0.05% are generallysatisfactory for most purposes. The additives may be added directly tothe fuels or may be incorporated into a suitable hydrocarbon solventwhich is then added to the fuels.

The effectiveness of the additive materials of the invention may bereadily seen from the following examples.

EXAMPLE I Polybutene having a molecular weight averaging about 1100 bythe Staudinger method was treated with 10% by weight of P 8 at atemperature of 425 F. for a period of about 8 hours. The resultingphosphosulfurized polybutene contained 3.32 weight percent sulfur and1.84 weight percent of phosphorus. One hundred grams of this materialwas then mixed with 87.4 grams of an aqueous solution containing 10weight percent of tctraethyl ammonium hydroxide. One hundred and fiftycc. of benzene were added to the reaction mixture and the mixture wasthen refluxed at a temperature of about 175 F. for 4 hours during whichtime the water was removed by azeotropic distillation. Benzene wasremoved by vacuum distillation. The resultant product had a clear ambercolor. Analysis showed it to be the tetraethyl ammonium salt of thephosphosulfurized polybutene.

The tetraethyl ammonium salt of a P S -treated bright stock was preparedin a similar manner, utilizing a bright stock which had a viscosity of150 Saybolt Universal seconds at 210 F. This oil was phosphosulfurizedby treating with 10% by weight of P 8 and the product was reacted withan equimolar quantity of tetraethyl ammonium hydroxide.

The tetra-n-propyl ammonium salt of phosphosulfurized polybutene wasprepared in the same manner used to prepare the tetraethyl ammoniumabove except that tetran-propyl ammonium hydroxide was utilized in placeof tetraethyl ammonium hydroxide.

The trimethylphenyl ammonium salt of phosphosulfurized polybutene wasprepared in a similar manner by treating the phosphosulfurized butenewith trimethylphenyl ammonium hydroxide.

EXAMPLE II The materials prepared in the previous example wereincorporated into samples of a middle distillate heating oil additive;

in concentrations of 0.01 weight percent. Typical properties of such aheating oil are as follows:

Gravity, API 32 Color, Tag Robinson 13 Flash, "F 150 Sulfur, percent 0.8Aniline point, F 137 Distillation, F.

IBP 330 FBP 645 The samples thus prepared, together with a sample of theoil containing no additive, were then subjected to an acceleratedstorage stability test which comprised heating the samples for a periodof 16 hours at a temperature of 210 F. At the end of this period, thesamples were filtered through sintered glass filters and the weight ofsediment collected from each sample was determined. The data obtained inthis test are shown in the following table:

Table I ACCELERATED STORAGE STABILITY TEST From the above table it canbe seen that the tetraalkyl ammonium salts of phosphosulfurizedhydrocarbons are excellent stabilizing additives for middle distillatefuels.

-The data also show that a similar material wherein a phenyl group wassubstituted for one of the alkyl groups in the ammonium radical did notpossess stabilizing qualities and instead resulted in the formation ofconsiderably more sediment than was formed in the oil containing noEXAMPLE III I In order to further demonstrate the invention, an aminesalt of a phosphosulfurized polybutene was prepared by treating aportion of the polybutene used in preparing the materials of Example Iwith P 8 in the manner described and then reacting the product with anequimolar quantity 'of tertiary butyl amine. This was then subjected toan accelerated storage stability test as described in Example II. Theresults are shown in Table II below:

7 Table II ACCELERATED STORAGE STABILITY TEST Fuel: Sediment, mgms./ 600gms. Base heating oil 17.9 Base heating oil+0.05 wt. percent of tertiarybutyl amine salt of P 8 treated polybutene; 23.8

The'above data indicate that the stabilizing properties previouslydemonstrated are peculiar to the tetraalkyl ammonium salts of thephosphosulfurized hydrocarbons and that amine derivatives ofphosphosulfurized hydrocarbons and that amine derivatives ofphosphosulfurized hydrocarbons do not possesses such stabilizingproperties.

EXAMPLE IV The eifect of the additive materials of the invention uponpotential sediment in middle distillate fuels can be i seen from thedata obtained in the potential sediment test. A sample of a heating oilsimilar to those employed in Examples 11 and III and a sample of thesame oil to which had been added 0.01 wt. percent of the tetraethylammonium salt of the P 5 treated polybutene were heated in glass bombsat a temperature of 100 F. for 24 hours. The sediment which formed ineach sample was then measured. The data obtained are as follows:

Table III POTENTIAL SEDIMENT TEST From the above it can be seen that thetetraalkyl ammonium salt of the phosphosulfurized hydrocarbonsignificantly reduced the potential sediment in the oil.

It will be understood that the additive materials of the presentinvention may be incorporated into petroleum distillate fuels inconjunction with other additive materials intended to overcome otherfuel deficiencies such as rusting, corrosion and the like.

What is claimed is:

1. An improved petroleum distillate fuel boiling in the range betweenabout 300 F. and about 900 F. to which has been added from about 0.001%to about 5% by weight of a tetraalkyl ammonium salt of aphosphosulfurized hydrocarbon, the alkyl groups in the ammonium radicalof said salt each containing from 1 to about 4 carbon atoms.

2. A fuel as defined by claim 1 wherein said salt is i0! present in aconcentration between about 0.001 and about 2% by weight.

3. A fuel as defined by claim 1 wherein said salt is a tetraalkylammonium salt of a phosphosulfurized petroleum bright stock.

4. A fuel as defined by claim I wherein said salt is a tetraethylammonium salt.

5. An improved petroleum distillate fuel boiling between about 300 F.and about 900 F. having incorporated therein from about 0.001% to about5% by weight of a tetraalkyl ammonium salt of a phosphosulfurizedpolyolefin having a molecular weight between about 800 and about 20,000,the alkyl groups in the ammonium radical of said salt each containingfrom 1 to about 4 carbon atoms.

6. A fuel as defined by claim 5 wherein said salt is present in aconcentration between about 0.005 and about 0.05% by weight.

7. A fuel as defined by claim 5 wherein said polyolefin is apolyisobutylene.

8. A petroleum distillate fuel boiling between about 300 F. and about900F. stabilized by the addition thereto of from 0.005 to 0.05 wt.percent of a tetraethyl ammonium salt of a P S -treated polyisobutylenehaving a molecular weight of from about 800 to about 10,000.

References Cited in the file of this patent UNITED STATES PATENTS2,534,217 Bartleson Dec. 19, 1950 2,636,858 Jones et a1 Apr. 28, 19532,688,612 Watson Sept. 7, 1954 2,712,528 Hill et al. July 5, 19552,768,999 Hill Oct. 30, 1956

1.AN IMPROVED PETROLEUM DISTILLATE FUEL BOILING IN THE RANGE BETWEEN ABOUT 300*F. AND ABOUT 900*F. TO WHICH HAS BEEN ADDED FROM ABOUT 0.001% TO ABOUT 5% BY WEIGHT OF A TETRAALKYL AMMONIUM SALT OF A PHOSPHOSULFURIZED HYDROCARBON, THE ALKYL GROUPS IN THE AMMONIUM RADICAL OF SAID SALT EACH CONTAINING FROM 1 TO ABOUT 4 CARBON ATOMS. 